BIOLOGY Feeding habits of the shortnose guitarfish, Zapteryx brevirostris (Müller and Henle, 1841) (Elasmobranchii, Rhinobatidae) in southeastern Brazil Marion, C.a*, Vaske-Junior, T.a, Gadig, OBF.a and Martins, IA.b aLaboratório de Biologia e Taxonomia de Chondrichthyes, Universidade Estadual Paulista “Júlio de Mesquita Filho” – UNESP, Campus Experimental do Litoral Paulista, Praça Infante Dom Henrique, s/n°, CEP 11330-900, São Vicente, SP, Brazil bUniversidade de Taubaté – UNITAU, Av. Tiradentes, 500, CEP 12030-180, Taubaté, SP, Brazil *e-mail: [email protected] Received February 1, 2010 – Accepted June 14, 2010 – Distributed February 28, 2011 (With 3 figures) Abstract The feeding habits of the shortnose guitarfish, Zapteryx brevirostris, were studied based on 382 specimens from the northern São Paulo coast, southeast Brazil. The diet showed a predominance of crustaceans (carideans and amphipods), polychaete annelids, and occasionally small fish, sipunculids, and cephalopods. The diets of males and females were similar; however, differences in the proportion of prey items were found among juveniles, subadults, and adults. Differences in the ingestion of prey items were found during the year, probably influenced by oceanographic parameters, although in general, the species feeds mostly on crustaceans and polychaetes. Keywords: Batoidea, diet, stomach contents, São Paulo. Hábito alimentar da raia-viola-de-focinho-curto, Zapteryx brevirostris (Müller e Henle, 1841) (Elasmobranchii, Rhinobatidae) no sudeste do Brasil Resumo Foram estudados os hábitos alimentares da raia-viola-de-focinho-curto, Zapteryx brevisrostris, com base em 382 espécimes coletados no litoral norte de São Paulo, sudeste do Brasil. A dieta mostrou predominância de crustáceos (carídeos e anfípodes), anelídeos poliquetos e ocasionalmente pequenos peixes, sipunculídeos e cefalópodes. A dieta de machos e fêmeas mostrou-se similar, entretanto, juvenis, subadultos e adultos demonstraram diferenças na composição de presas. As frequências dos itens diferiram ao longo do ano, provavelmente influenciadas por fatores oceanográficos, embora, em geral, a espécie se alimente predominantemente de crustáceos e poliquetos. Palavras-chave: Batoidea, dieta, conteúdo estomacal, São Paulo. 1. Introduction Elasmobranch fishes are top predators, feeding on a of basic aspects of their biology which is important to wide range of prey items. The feeding habits of batoids understand the dynamics and ecology of populations and (skates and rays) involve predation on benthic communities, communities (Krebs, 1998). especially on small- to medium-sized fish and numerous Members of the f Rhinobatidae, distributed mostly invertebrate taxa (Ellis et al., 1996). Along the Brazilian along tropical coastal waters of the Atlantic, Indian and coast, a few batoid species are caught for commercial Pacific Oceans, are often important components of coastal purposes, mostly as bycatch of the shrimp trawling and marine ecosystems (Kyne and Bennett, 2002). They gillnet fisheries (Graça Lopes et al., 2002; Chaves et al., 2003). live in shallow tropical and subtropical coastal waters Batoid feeding habits have been the subject of several of all oceans, with four genera and 40 species known. studies (McEachran et al., 1976; Muto et al., 2001; (Bigelow and Schroeder, 1953; McEachran and Carvalho, Brickle et al., 2003; Braccini and Perez, 2005; Robinson et al., 2002). In Brazil, two genera and four species are known: 2007; Moura et al., 2008). The study of feeding ecology Zapteryx brevirostris (Müller and Henle, 1841); Rhinobatos and habitat use of these fishes provides the knowledge percellens (Walbaum, 1792); Rhinobatos horkelli Müller Braz. J. Biol., 2011, vol. 71, no. 1, p. 83-89 83 Marion, C. et al. and Henle, 1841; and Rhinobatos lentiginosus Garman, possible and quantified from their remains (e.g., complete 1880 (Menezes et al., 2003). prey items, otoliths, skull bones, crustacean exoskeletons) The shortnose guitarfish Zapteryx brevirostris is a according to Braga et al. (2005), Costa et al. (2003), small endemic species, about 550 mm in total length, and Amaral and Nonato (1996). Only a few individuals inhabiting sandy bottoms of coastal waters (2 to 60 m could be identified to species level, but because of their deep), in the western South Atlantic, from Rio de Janeiro importance as food items they are included in Table 1. to Argentina (Figueiredo, 1981; Carvalho Filho, 1999). It Prey items are listed by taxonomic criteria, at the lowest is a viviparous lecithotrophic species, producing between taxonomic level possible. two and eight embryos per litter, measuring 130 to 160 mm In order to determine differences (seasonal and in total length (Batista, 1992). Males and females mature ontogenetic variations) of prey consumed, the Kruskal- at 400-473 mm and 370-522 mm, respectively (Batista, Wallis test was used (Zar, 1999). The Mann-Whitney U 1992; Abilhoa et al., 2007). Despite the wide distribution test with a Bonferroni adjustment was used to compare and abundance in the Brazilian coast, trophic aspects of feeding of females and males. Statistical analyses were Z. brevirostris are poorly known, representing an obstacle conducted with PAST version 1.99. All statistical tests for implementations of actions aimed at the management used a significance level of 5%. and conservations of natural resources. Morisita’s Simplified Index of Similarity adapted by A few studies deal with the feeding biology of Horn (1966) was used with the statistical routine PAST Z.brevirostris, such as the study by Castello (1971), 1.99 (Hammer and Harper, 2003), to assess the possible in which the diet represented only a percentage of the feeding overlap among major zoological groups (crustaceans, organisms found in the stomach, Soares et al. (1992) polychaetes, fish, and cephalopods). According to Langton compared the feeding habits of Z. brevirostris with five other (1982), values obtained by the overlap index range from species of rays collected along the inner shelf of Ubatuba, 0 to 1; values between 0 and 0.29 indicate low overlap; Bornatowski et al. (2005) studied the food composition of values between 0.30 and 0.59 indicate partial overlap; this species captured on the coast of Santa Catarina and and values between 0.60 and 1.0 indicate a high overlap Barbini (2006) researched in the Buenos Aires Province between diets. and Uruguay coast. Prey diversity was calculated for all seasons, using Because of the sparse available information on trophic the Shannon–Weiner index (Zar, 1999), with PAST 1.99 aspects in different seasons and during ontogeny, the (Hammer and Harper, 2003). These indices were calculated present study analysed the dietary changes with seasonal for the species and major groups. variables and ontogeny, and compared the diets of males The diets from the two areas were analysed separately. and females of Z. brevirostris caught on the northern São However, because they did not differ significantly (p < 0.05), Paulo coast, southeast Brazil. the data were pooled. 2. Materials and Methods 3. Results The study was conducted in two regions, Ubatuba, The maturity categories used were juveniles (23º 26’; 23º 31’ S and 44º 55’; 45º 03’ W) and Caraguatatuba (134-408 mm), subadults (386-452 mm) and adults (23º 36’; 23º 43’ S and 45º 20’; 45º 00’ W). Ubatuba has (380-540 mm). A total of 382 individuals were analysed, an open shoreline, with several small islands; whereas measuring between 134 and 536 mm TL; of which 229 Caraguatatuba is located in a sheltered bay. were juveniles, 18 were subadults, and 135 were adults. The northern coast of Sao Paulo is subject to the The distribution of total length frequencies was bimodal, strongly seasonal influence of three water masses, which together modify the temperature, salinity, and nutrients, and consequently the presence and abundance of organisms (Carvalho Filho, 1999). Samples were obtained monthly between January and December 2002, along seven transects at depths between 5 and 35 m (Figure 1), from small shrimp trawlers. All specimens were measured for Total Length (TL) and dissected to check the gonad stage. Maturity categories were determined according to clasper calcification in the males and follicle maturation in the females, as described by Stehmann (2002). Stomachs were removed, frozen, and analysed in the laboratory. The importance of prey items was evaluated using the percentage frequency of occurrence (%FO) and Figure 1. Map of the sampling locations of Zapteryx the percentage in number (%NF) (Hyslop, 1980). Prey brevirostris at Ubatuba and Caraguatatuba, southeast coast species were identified to the lowest taxonomic level of Brazil. 84 Braz. J. Biol., 2011, vol. 71, no. 1, p. 83-89 Braz. J. Biol.,2011,vol.71, no.1,p.83-89 J. Braz. Table 1. Prey items of Zapteryx brevirostris: frequency of occurrence (%FO) and percentage in number (%NF) for the major prey taxa and identifiable dietary categories. Summer 01 n = 56 Autumn n = 49 Winter n = 138 Spring n = 113 Summer 02 n = 26 Total n = 382 %FO %NF %FO %NF %FO %NF %FO %NF %FO %NF %FO %NF Crustacea 99.5 87.9 Caridea Hippolytidae 53.4 10.8 70.0 43.1 91.3 66.9 61.1 16.2 50.0 4.3 71.1 41.6 Amphipoda 72.4 32.1 58.0 27.1 48.5 12.4 74.3 22.8 73.0 27.3 62.6 19.8 Gammaridea Ampelisca sp. Hiperiidae Caprellidae Cumacea Diastylidae 13.8 5.1 14.0 3.0 26.8 5.6 65.5 29.8 73.0 36.3 37.6 13.5 Brachyura 65.5 12.3 18.0 4.9 11.6 1.4 38.9 9.5 57.7 18.2 31.7 6.3 Portunidae Portunus sp. Dietary oftheshortnoseguitarfish Callinectes sp. Majoidea Libinia sp. Leucosiidae Persephona sp. Isopoda 43.1 7.7 26.0 3.8 22.4 3.6 33.6 8.8 26.9 3.8 29.6 5.3 Stomatopoda 5.2 0.6 4.0 0.0 0.0 0.7 4.4 0.3 7.7 0.5 3.1 0.2 Ostracoda 0.0 0.3 0.0 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Cladocera 0.0 0.0 0.0 0.1 2.0 0.0 0.0 2.0 0.0 0.0 0.0 0.0 Sergestoidea 0.0 3.5 0.0 0.3 4.0 0.5 5.0 0.5 8.8 0.0 4.1 0.5 Penaeoidea 0.0 0.0 0.0 0.0 0.9 0.3 5.8 0.7 4.4 0.9 4.9 0.4 Penaeidea Artemesia longinaris Rimapenaeus constrictus Xiphopenaeus kroyeri Sicyoniidae Sicyonia dorsalis S.